Apparatus for maintaining constant tension in a moving strand

ABSTRACT

Disclosed is an apparatus for maintaining a constant tension in a moving strand which comprises a rotatably mounted rigid support for two guides, the support being arranged between strandadvancing means having speed-regulator means and strand-takeup means with the support being disposed to provide an S-shaped strand path around the guides with tension in the strand producing a torque in a first direction; torquing means for applying a continuous rotational torque to the support in a direction opposite to the first direction; and position-sensing means for the support operably associated with the speedregulator means of the advancing means to maintain the support near an equilibrium position.

United States Patent [72] Inventor Billy G. Ferguson Hermitage, Tenn. [2 l] Appl. No. 779,017 [22] Filed Nov. 26, 1968 [45] Patented Jan. 19, I971 [73] Assignee E. I. du Pont de Nemours and Company Wilmington, Del. a corporation of Delaware [54] APPARATUS FOR MAINTAINING CONSTANT TENSION IN A MOVING STRAND 7 Claims, 3 Drawing Figs.

[52] US. Cl. 226/25, 226/195 [5 1] Int. Cl. B65h 23/10 [50] Field of Search 226/25, 42, 44, H3, 114, 30, I95

[56] References Cited UNIT ED STATES PATENTS 3,2 2 5,989 12/1965 Stine 3,326,436 6/1967 Huck 3,384,281 5/1968 Mason Primary Examiner-Richard A. Schacher Assistant Examiner-Gene A. Church AttorneyE. Leigh Hunt ABSTRACT: Disclosed is an apparatus for maintaining a constant tension in a moving strand which comprises a rotatably mounted rigid support for two guides, the support being arranged between strand-advancing means having speed-regula- PATENTEUJANIQIQ?! 31555359 BILLYIGY FERGUSON aw/1&7

ATTORNEY variability is less,than-satisfactory;s t

BAcxoRounDor THE iNvizNrioiv.

l.FieldoftheInvention This invention relates "to i a tension-maintaining apparatus and more particularly. toapparatusjfo'r maintaining constant tensioninamovingstrand. t I

2; Description of the Prior -Art In the commerciz'ilmanufactureof synthetic textile fibers. it

' is customary. to wind and'unwind strands at very high speeds.-

At various stages in the processes of feeding and withdrawing strands from'production steps, it isnjecessary to hold the tension at a constant value; Fort instance, in the process of cutting continuous. filaments to staple when feeding. thefilaments to a centrifugal-type cutter, if'strandtension varies, the cut length FOR- MMNTAINING CONSTANT TENSION I of the.staple varies accordingly, a condition oftenleading to I unsatisfactory performance. of "the .fibersin drafting to yarns and undesirable defects in'fabrics knitted orlwoven-therefrom. The effects of inadequate,- tension con'trol are felt more -'seri-' ously when dealing with a stretch-type yamJ eit-her crimped in configurationorofthespandextype. f

There have-been many qtension-maintaining .devices proposed -in thepast ranging-from simpleypairs of snubbing pins over which athreadline passes in. frictional contact to highly sophisticated and; ofteritimes prohibitively expensive; electronic .threadline monitoringsysterns. Wholtonin U S.-

Pat. No. 2.3; 2: 6,"ll }fproposes afsimple. inexpensive system'for maintaining constant strandten'sion 'lQOflSiSling of two fixed -"mea nsrefers to the last fixed'guide that controls the V strand before 0. Likewise. the t'akeup means of 5 includes any strandguides arranged between Ii and (and any reference to the location of the takeup means refers to the guide thatis closest to c. a v

The preferred-advancing means a isu direct current electric motor with the regulator'meansbeing an electric circuit that is responsive to the 'positi'omsensing means of t' which is a vari bleresistorq I r 1 It is preferred that the pivot for the rigid support in c is midway between advancing means a and takeup means Ii and each strand guide is mounted an equal distance from the pivot and arranged in a straight line with said pivot.

lt is preferred that the torquing means dcomprises a' fluidcylinder being pivotally attached to a second fixed element with the point of thea ttachment being in line withsaid'guides when the support is in equilibrium positionand at a distance from thepivot of the rigid support that is equal to the distance of each guide from advancing means a and tak'eup means b. n

guides and betweenthem. two mo vable guides attached to a I member which. is "free to rotate aboutan axis. However, especially as the need isofelt of iate formorean dv more accuracy in finished products and, greater efficiency in manufacturing processes, in .this and otherfgsimilar devices of the art,:tension SUMMARY} T'i enivENnoN an apparatus for maintaining a constant tension in an advancirig strand comprisingin'combination: i a. strand-advancing means" including"speed-regulator means v b. strand-takeup'means arranged tota keup and forward the strand advanced byth e strand advancing means;

a rigid support rotatablyrnounted o'n'a fixed pivot'located guide members spaced from the pivot of the rigidsupport and being disposed such that aline connecting the'two sion toprovide an angular rotation of said rigid member about the pivot when a differential in strand tension from the preselected tension exists; and

associated with the speed-regulator means of a and adapted to increase the speed of advancing means a if said support moves in said first direction to allow the supp rt to return to afdesired equilibrium position said: sensing-means and speed-regulator means of a likewise being adapted to decrease the speed of advancing means a if said support moves in a direction opposite to said first direction to allow'said support to return to the desired equilibrium position. ltmust be understood that the :ad-

vancing means 0 includes any fixed strand guides located before c. Any reference to location of the advancing :betweenti and b said support'h'aving two'rnounted'strand position-sensing means for said support that is operably The apparatusof thisinvention'is particularlydescribed'las 50 I the present invention.

wheneveritheapparatusiis at'o'perating equilibrium it is preferred that a line connecting theguides is at substantially a 90 angle with respect to a line connecting advancing means a andtakeup meansb.. v

The term strand refers to: filaments, monofilaments, any ordered assemblage of textile fibers or sheets having a high ratio'of "length; to diameter 'or' thickness "including slivers. rovings, single ya'rnsgplied yarns. cords; threads.'bi'aids. ropes; tows.'sheets, etc. i

I BRIEF DESCRlFTlON oFIHE DRAWINGS In the accompanying drawings: t FIG. 1 isa perspective view of the new tensioningdeyice; 1 FIG. 2 is a detailed view of the pushrod pivotassembly of FICLL' 1' I FIG. 3 is a plan view of an embodiment of-theapparatus of DESCRlPIlON bF'THE PREF nREo MBODIMENTs 7 In describing the preferred embodiments of the inventionillustrated in the drawings,specific terminology will be restored to for the sake of'clarity; -however,=-it isinot intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

With reference to FIG. 3, the invention is described as an apparatus-for maintaining constant tension in a longitudinally moving strand, comprising strand-forwarding means and strand-takeup means and situated therebetwee'n firstand second strand-guide members for changing the direction of travel of the strand path as it passes in arcuate contact therewith to form points'of tangency a and b respectively,and

situated therebetween a rigid support mounted to rotate about a central axis running transverse to the strand path at point p which is equidistant from a andb and lies along a straight line joining a and b,said rigid support having, axially protruding therefrom, two oppositely mounted, cylindrical strand-guide members which are equispaced from said central axis, said cylindrical, axially protruding guide members having surface points 0 and d respectively which lie at the intersection of the threadline with a straight line extending from p throughltheir axes of symmetry, and a fluid-operated push rod pivotally mounted at a pivot point q on a rigid pushrod support, q being at a distance X from p. and extending from said pivot point to 1 a third rotatable member axiallyl'protruding from said rigid support, the contact of said pushrod with said third member being tangential having point of tangency e,the arrangement of components being such that the moving threadline passes from said feed means partly around said first strand-guide member, partly around each of said axially protruding, cylindrical guide members in an S-shaped path, thence partially around said second strand-guide member to said strand takeup means, provided that the distance up is substantially equal to the distance pb which, in turn, is substantially equal to X and the distance ad is substantially equal to cb which is substantially equal to the distance eq at all times during the tension-maintaining operation, said pushrod maintaining a torque arm relative to p upon said rigid support which is substantially equal to the sum of the two identical torques of the threadline tension relative to point p, all three of which tend to rotate said rigid support about p and this torque equalization holding for any deflection of said rigid support about p throughout the tension-maintaining operation.

In the drawings, in which like numbers of reference are used to designate like components, FIG. 1 illustrates strand 10 being forwarded by driven roller 12 (motor not shown) and associated roller 11, passing partly around first stationary strand-guide member 13 and then in an S'shaped path passing partly around strand-guide members l4, l and 16, and then passing to takeup means comprising driven rollers 17 and 17' (motor not shown). Strand-guide members 14 and 15 are mounted on opposite ends of rigid support 18 and are equidistant from pivot point 19 about which support 18 is free to rotate. Rigid support 18 is rotatably mounted on bar 20 which is fixedly mounted to rear support 21, shown in part. Pneumatically loaded pushrod 22 is pivotally mounted by means of pin 23 to stationary support 24, shown in part. F lexible tube 25 connects an external source of air pressure to cylinder 32. Pushrod 22 makes contact with pivot assembly 26. Variable resistor 33 is responsive to the position of support 18 and regulates the speed of the advancing means (motor not shown) to keep support 18 near the desired equilibrium posi tion.

In FIG. 2 it is seen that pushrod pivot assembly 26 includes axially protruding wheel member 27 and, fixedly attached thereto, a rigid member 28 which firmly embeds the arm of pushrod 22. Wheel 27 is free to rotate about pin 30.

In operation, longitudinally moving strand having varying tension makes an S-shaped path around guide members 14 and 15. As shown in FIG. 1, pushrod 22 exerts force according to its air supply pressure against the pivot point of assembly 26 which effects a torque on rigid support 18. Thus, as strand tension lessens between guides 13 and 16, rod 22 will exert torque on rigid support 18 and cause it to move in a counterclockwise fashion until the torque about point p on rigid sup port 18 exerted by the strand equally opposes it. Although not necessary, there may be substantial frictional contact between the strand and guides 14 and I5; operation with rotatable guides is explained below. Likewise, as tension increases on the strand, rigid support member 18 is caused to move in a clockwise manner until the torque exerted on support 18 by the strand about point p is equal and opposite to the torque exerted by rod 22 acting on rigid support 18 about point p.

In order for the new apparatus to function properly, there are certain principles regarding relative spacing of its important structural members. These are best understood by reference to FIG. 3. In FIG. 3, it is seen that point of tangency a and b are formed by passage of strand 10 in contact with the respective guide members. Point of tangency a in the drawings in that point at which the strand leaves member 13, and point of tangency b in the drawings is that point at which the strand just touches member 16. Guide members 14 and are equispaced from central axis 19 of rigid support 18, about which axis rigid support 18 is free to rotate. Point p is along the axis of rotation 19 of rigid support 18 and lies a straight line joining points a and b and is equidistant from a and b. Points c and d are located at the point of intersection of the strand with a straight line extending from p through the axis of symmetry of cylindrical guide members 14 and 15 respectively. The pneumatically loaded pushrod exerts force along line 29, which extends to point of tangency c with axially protruding wheel 27. Axially protruding member 27 is mounted to rotate about its axis so that upon rotation of rigid support 18, a force acting along line 29 is always at a tangent to axially protruding member 27 at the point of tangency c. A pushrod pivot point q is located at point 23. Thus, it is seen that the distance up is substantially equal to the distance pb, which is substantially equal to qp, and the distance ad is substantially equal to cb, which is substantially equal to eq. The foregoing relationships are preferably in the practice ofthe invention.

The specifications concerning geometry of the members 4 relative to each other is important because the torque relative to point p of the pushrod exerting force along line 29 on rigid support 18 is to be equal to the sum of the two identical torques of the strand tension relative to point p, all three of which tend to rotate rigid support 18 about point p. Moreover, this relationship should follow for any deflection of rigid support 18 about point p. This relationship is important in reducing strand-tension variations. In structurally similar devices of the prior art, this relationship does not hold true, a condition which causes unsatisfactory control of strand tension.

The new device has the advantage of not only maintaining a given tension at a constant value but of being readily adjustable to maintain other tensions constant. This may be accomplished merely by adjusting the air supply pressure to the pneumatic pushrod.

The advantages of the new operation are numerous and it is especially accurate in maintaining constant tension on a moving strand.

It is to be understood that the form of the invention herein shown and described is to be taken as a preferred embodiment. Various changes may be made in the shape, size, and arrangement of parts. For example, the protruding member 27 may be on the same side of rigid support 18 as the guides 14 and 15 or on a different side. Pivot point q may be at any point around rigid member 18 provided its distance from p is in general accordance with the teachings set forth hereinabove. The guide members may be rotating cylinders and the bar 20 may be connected to a variable resistance potentiometer which can be used to control the relative rotational speeds of guide members 13 and 16 which in turn may be associated with rollers to form strand nip-points at a and b In such a device the position of guide members 14 and 15 may be maintained substantially constant with changes in threadline tension between points a and b; if threadline tension increased it would tend to cause rigid support 18 to rotate against the opposing force of pushrod 22, the variable resistance potentiometer would signal one or both of the motors driving guide members 13 or 17 and cause consequent adjustment of their rotational speed to compensate for the varying tension.

The present invention is useful in controlling tension variation in monofilaments and multifilaments as well as staplespun yarns and tow.

lclaim:

1. An apparatus for maintaining a constant tension in an advancing strand comprising in combination:

a. strand advancing means including speed regulator means:

b. strand takeup means arranged to takeup and forward the strand advanced by the strand-advancing means;

c. a rigid support rotatably mounted on a fixed pivot located between said strand-advancing means and said strandtakeup means, said support having two mounted strandguide members spaced from the pivot of the rigid support and being disposed such that a line connecting the two guides is at a substantial angle to a line connecting said strand-advancing means and said strand takeup means to provide a S-shaped strand path around said guides with tension in the strand producing a rotational torque about said pivot in a first direction;

d. torquing means for applying a continuous rotational torque about said pivot of a preselected magnitude in a direction opposite to said first direction, the magnitude being equal to the torque produced by the strand when passing about said guides with the strand at a desired preselected tension to provide an angular rotation of said rigid member about the pivot when a differential in strand tension from the preselected tension exists; and position sensing means for said support that is operably associated with the speed-regulator means of said strandadvancing means and adapted to increase the speed of said strand-advancing means if said support moves in said first direction to allow the support to return to a desired equilibrium position that corresponds to the preselected strand tension, said sensing means and speed regulator means of said strand-advancing means likewise being adapted to decrease the speed of said strand-advancing means if said support moves in direction opposite to said first direction to allow said support to return to the desired equilibrium position.

2. The apparatus as in claim 1 wherein the strand-advancing means includes a direct current motor electrically coupled by a circuit to an associated power supply and the speed regulator means comprises a variable resistor operatively arranged in the circuit.

3. The apparatus as in claim 1 wherein the pivot for said rigid support is midway between said strand-advancing means and said strand-takeup means and each strand guide is mounted an equal distance from the pivot and arranged in a straight line with said pivot.

4. The apparatus as in claim 3 wherein said torquing means comprises a fluid-operated pushrod pressure cylinder having the exterior end of the rod pivotally attached to the rigid support at a point on a line passing through a pivot being at a angle with respect to a line connecting each guide and the rod is located a perpendicular distance from the supportpivot that is equal to the distance of each guide from said pivot, the opposite cnd'of the cylinder being pivotally attached to a second fixed element with the point'of the attachment being in line with said guides and at a distance from the pivot ol the rigid support that is equal to the distance of each guide from said strand-advancing means and said strand-takeup means.

5. The apparatus as in claim 4 wherein said guides are rollers.

6. The apparatus as in claim 5 wherein the exterior end of the rod is offset from the point of attachment to the rigid support by a distance equal to the guide roller radius.

7. The apparatus as in claim 4 wherein at equilibrium a line connecting the guides is at substantially a 90 angle with respect to a line connecting said strand-advancing means and said strand-takeup means. 

1. An apparatus for maintaining a constant tension in an advancing strand comprising in combination: a. strand advancing means including speed regulator means: b. strand takeup means arranged to takeup and forward the strand advanced by the strand-advancing means; c. a rigid support rotatably mounted on a fixed pivot located between said strand-advancing means and said strand-takeup means, said support having two mounted strand-guide members spaced from the pivot of the rigid support and being disposed such that a line connecting the two guides is at a substantial angle to a line connecting said strand-advancing means and said strand takeup means to provide a S-shaped strand path around said guides with tension in the strand producing a rotational torque about said pivot in a first direction; d. torquing means for applying a continuous rotational torque about said pivot of a preselected magnitude in a direction opposite to said first direction, the magnitude being equal to the torque produced by the strand when passing about said guides with the strand at a desired preselected tension to provide an angular rotation of said rigid member about the pivot when a differential in strand tension from the preselected tension exists; and e. position sensing means for said support that is operably associated with the speed-regulator means of said strandadvancing means and adapted to increase the speed of said strand-advancing means if said support moves in said first direction to allow the support to return to a desired equilibrium position that corresponds to the preselected strand tension, said sensing means and speed regulator means of said strand-advancing means likewise being adapted to decrease the speed of said strand-advancing means if said support moves in direction opposite to said first direction to allow said support to return to the desired equilibrium position.
 2. The apparatus as in claim 1 wherein the strand-advancing means includes a direct current motor electrically coupled by a circuit to an associated power supply and the speed regulator means comprises a variable resistor operatively arranged in the circuit.
 3. The apparatus as in claim 1 wherein the pivot for said rigid support is midway between said strand-advancing means and said strand-takeup means and each strand guide is mounted an equal distance from the pivot and arranged in a straight line with said pivot.
 4. The apparatus as in claim 3 wherein said torquing means comprises a fluid-operated pushrod pressure cylinder having the exterior end of the rod pivotally attached to the rigid support at a point on a line passing through a pivot being at a 90* angle with respect to a line connecting each guide and the rod is located a perpendicular distance from the support pivot that is equal to the distance of each guide from said pivot, the opposite end of the cylinder being pivotally attached to a second fixed element with the point of the attachment being in line with said guides and at a distance from the pivot oF the rigid support that is equal to the distance of each guide from said strand-advancing means and said strand-takeup means.
 5. The apparatus as in claim 4 wherein said guides are rollers.
 6. The apparatus as in claim 5 wherein the exterior end of the rod is offset from the point of attachment to the rigid support by a distance equal to the guide roller radius.
 7. The apparatus as in claim 4 wherein at equilibrium a line connecting the guides is at substantially a 90* angle with respect to a line connecting said strand-advancing means and said strand-takeup means. 